The present invention relates in general to mineral mining installations, especially longwall installations, and to roof support systems usable in such installations.
In the field of mine installation roof support systems are known in a whole variety of constructions. Usually, however, conventional roof support systems are composed of individual chocks or units, with hydraulic props interposed between roof and floor-engaging structures. Shifting rams connect the units to a scraper-chain conveyor and serve to advance the latter, usually with a machine guide. The units can follow up the working progress by retraction of the shifting rams. During the shifting of the support units the props are retracted or at least partially relieved and this can leave comparatively large areas of the roof temporarily unsupported. In longwall workings, it is common to advance the conveyor and guide means after each passage of the cutting machine or plough and to draw up the support units in short steps. The repeated support and relief of the roof often leads to problems.
A general object of this invention is to provide support systems and units which will at least mitigate some of these problems.